Democrats have a surprisingly competitive race for their presidential nomination, and if you watched their announced candidates debate Tuesday night, you saw why. Not because the candidates, like their Republican counterparts, spent much time and effort attacking one another; they didn't. And not because Hillary Rodham Clinton suffered grievous wounds or damaged her standing; she didn't.

No, what came closest to electrifying the night was a Vermont senator, a self-described democratic socialist who honeymooned in the Soviet Union, and who probably can't get elected president. Bernie Sanders demonstrated time and again Tuesday night why he's the force vector in this race. If you watched, you now know why he attracts the huge crowds, the money, the energy of rank-and-file Democrats — a party to which he doesn't even belong.

You also know why he gives Clinton conniptions. While she behaved like the front-runner — confident, competent, comfortable — Sanders was connecting with the audience. He even managed to profit from a Clinton problem while tacitly excusing her from it: "The American people," he said, "are sick and tired of hearing about your damn emails!" Sanders wanted to talk about issues that trouble Americans.

Clinton surely believes she had a good night. But her answer to the first question — essentially, given her flip-flops, would she say anything to get elected? — betrayed her agenda: the cautious politics of addition. She first pivoted to an earnest non sequitur; she would, she said, heal an America riven by economic inequality, racial divides, gender inequities. Pressed on whether she would commit to being a progressive or a moderate, she straddled: "I'm a progressive, but I'm a progressive who likes to get things done."

Sanders, though, had a better night. Much as Republican debates showcased Donald Trump, this debate showcased Sanders' authenticity. The notion of anyone asking if he would change positions to win votes is preposterous.

Sanders is the reason Democrats have a serious primary race. And he came across Tuesday night as a candidate who believes what he believes and won't waffle. He voiced positions that will give some Democrats pause; he isn't a pacifist, he said, and as commander in chief wouldn't hesitate to take America to war. Clinton, meanwhile, answered a challenge to her Senate vote for war in Iraq not with a defense or an apology, but by invoking President Barack Obama: Even after that vote, he chose her as secretary of state. Sorry, but it sounded lame.

Photo gallery: First Democratic presidential debate

The night was more decorous, less rowdy, than the GOP jousts. The other three participants — former Maryland Gov. Martin O'Malley, former Rhode Island Sen. and Gov. Lincoln Chafee and former Virginia Sen. Jim Webb — were minor players before the debate and emerged much the same. The night's big mystery was the man who wasn't there:

Leave it to wily Fox News to steal some thunder from CNN's debate. Earlier Tuesday, Fox unveiled poll results that had Vice President Joe Biden trailing Clinton for the nomination, "yet he looks more electable than the former secretary of state against top Republicans." In hypothetical matchups, every top-tier Republican leads Clinton. Biden? Even without entering the race, or joining the debate, he leads each of those Republicans.

Hillary Clinton came out smiling. She used her opening statement in the first debate of Democratic candidates Tuesday to remind people of her not-always-apparent humanity: She's grandmother to a 1-year-old, and also a mother, daughter, and on and on. Paid family and medical leave? She's for it.

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Hillary Clinton came out smiling. She used her opening statement in the first debate of Democratic candidates Tuesday to remind people of her not-always-apparent humanity: She's grandmother to a 1-year-old, and also a mother, daughter, and on and on. Paid family and medical leave? She's for it.

... (Margaret Carlson)

Clinton's sturdy performance certainly didn't diminish the prospect of Biden any more than she diminished Sanders. So what happens now?

The Democrats don't have another debate until Nov. 14. Will Biden be with them in Des Moines? Or is this Clinton vs. Sanders — the careful politician who has spent a career prepping for this campaign and the intriguing threat to her long-assumed nomination?